“Texas medicine” is a nickname for mescaline (a drug from the cactus plant) that Bob Dylan used in his song, “Stuck Inside of Memphis with the Memphis Blues Again.” The song appears on the Dylan albums Blonde on Blonde (1966) and Bob Dylan’s Greatest Hits Vol. II (1971).
 
The term “Texas medicine” has been very rarely used and almost all uses refer to Bob Dylan’s lyrics.
 
   
Wikipedia: Stuck Inside of Mobile with the Memphis Blues Again
“Stuck Inside of Mobile with the Memphis Blues Again” is a song by Bob Dylan that appears on his 1966 album Blonde on Blonde. The album version also appears on 1971’s Bob Dylan’s Greatest Hits Vol. II. Another version of the song appears on the 1976 live album ,i>Hard Rain, and was also released as a single with Rita May as the B-side. An early studio take, done in a faster cut-time, was released on The Bootleg Series Vol. 7: No Direction Home: The Soundtrack; as the recording indicates, Dylan had difficulty fitting the words to the tempo, and evidently this led to its rearrangement, as heard on the official album, in a more “rock” oriented 4/4 time.

The song also inspired the name of the Memphis Group, a 1980s design movement, with its title.
 
Wikipedia: Mescaline
Mescaline or 3,4,5-trimethoxyphenethylamine is a naturally-occurring psychedelic alkaloid of the phenethylamine class. It is mainly used as an entheogen, and as a tool to supplement various practices for transcendence, including in meditation, psychonautics, art projects, and psychedelic psychotherapy.
 
It occurs naturally in the peyote cactus (Lophophora williamsii), the San Pedro cactus (Echinopsis pachanoi) and the Peruvian Torch cactus (Echinopsis peruviana), and in a number of other members of the Cactaceae plant family.
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Legality
In the US, mescaline was made illegal in 1970 by the Comprehensive Drug Abuse Prevention and Control Act.[14] It was prohibited internationally by the 1971 Convention on Psychotropic Substances and is categorized as a Schedule I hallucinogen by the CSA.
   
Urban Dictionary
texas medicine
slang for mescaline, used in Bob Dylan’s stuck inside of mobile with the memphis blues again
now the rainman gave me two cures,
Then he said, “Jump right in.”
The one was Texas medicine,
The other was just railroad gin.
An’ like a fool I mixed them
An’ it strangled up my mind,
An’ now people just get uglier
An’ I have no sense of time.
Oh, Mama, can this really be the end,
To be stuck inside of Mobile
With the Memphis blues again.
by glaush Jun 28, 2007